We have identified an adenovirus 2 (Ad2) coded early glycopolypeptide with apparent molecular weight of 20-21,000 (designated gp20/21K) (early genes are expressed before initiation of viral DNA replication). We propose to further characterize the biological, chemical, and physical properties of gp20/21K. It will be purified by affinity chromatography on concanavalin A-agarose followed by preparative sodium dodecyl polyacrylamide gel electrophoresis. High titer monospecific antisera will be prepared in rabbits, and will be used to study the biology of gp20/21K. Antibody experiments will include: (1) immunofluorescence and immunoelectron microscopy analysis of Ad2 early infected and transformed cells; (2) radioimmunoprecipitation and radioimmunoprecipitation-inhibition analysis throughout the course of productive infection, to document the regulation of the gp20/21K gene; and (3) attempts to inhibit Ad2 DNA synthesis in a soluble Ad2 DNA replication complex. Gp20/21K will be purified to homogeneity, using lectin and antibody-affinity procedures. The amino acid composition and peptide maps will be established, and the carbohydrate moiety investigated. The ultimate long-range goal of these studies will be to elucidate the function of gp20/21K in Ad2 replication, and to understand the transcription and translation mechanisms involved in the synthesis of gp20/21K, as well as the mechanisms by which expression of the gp20/21K gene is curtailed late after infection.